Plastic parts have seen many applications and continue to replace other materials as the material properties and the processes for manufacturing improve. One problem in manufacturing plastic parts, particularly for blow molded or rotationally molded parts is the cutting process into the final shape. A blow or rotationally molded part is only semi rigid. When pressure from a knife or blade is exerted onto the outside of a hollow blow molded or rotationally molded part, the knife or blade permanently deforms the part to such an extent that the part no longer is within manufacturing tolerances. The manufacturing tolerances may vary with different applications but can be relatively small. For example, duct components made for air movement in specialized machines such as paper copiers may have relatively small manufacturing tolerances.
In order to maintain the part within acceptable tolerances of deformation, other methods of cutting have been developed. One such method is with saw cutting. Saw cutting is a relatively slow process and it creates large quantities of plastic dust. Effort and expense must be spent to control and properly dispose of the plastic dust. Another method is a water jet cutting. Water jet cutting may reduce the plastic dust but only with the inconvenience of a watery mess that also needs to be controlled. Another method is with the use of a laser cutter. The use of a laser literally melts the plastic and burns through the plastic. Great care is needed to prevent discoloration due to charring of the plastic. Furthermore, it is very difficult to maintain a square edge during the laser cutting process due to the melting of the plastic.
What is needed is a economical cutting process that reduces deformation of a plastic part and provides a square edge to the finished part.